Character-indicating electron tube with fluorescent display structure

ABSTRACT

A fluorescent display tube of the triode construction is provided with an insulating substrate, an anode electrode including a plurality of fluorescent anode segments adapted to form characters and embedded in the insulating substrate, a single grid electrode disposed close to the anode segments and a filament in front of the grid electrode. The grid electrode is provided with a window common to the region of a pattern formed by the plurality of fluorescent anode segments and the window is provided with an electroconductive mesh.

l l i 1 I l Inventor Appl. No. Filed Patented Assignee Priority ite States Patent Mikiharu Tanji Ise, Japan Nov. 18, 1969 Nov. 9, 1971 Ise Electronics Corporation lse, Japan Dec. 10, 1968 Japan Continuation-impart of application Ser. No. 676,580, Oct. 19, 1967, now Patent No. 3,508,101.

CHARACTER-INDICATING ELECTRON TUBE WITH FLUORESCENT DISPLAY STRUCTURE 3 Claims, 7 Drawing Figs.

U.S.Cl 313/1095, 313/108 Int. Cl H01] l/62, HOlj 63/04 Field of Search 313/1095, 108, 86, 107.5

[56] References Cited UNITED STATES PATENTS 2,571,723 10/1951 Jonker etal. 313/1095 X 2,594,025 4/1952 Jacobi et al 3l3/l07.5 2,758,237 8/1956 Steinhardt 313/86 X 3,237,040 2/1966 Kupsky 3l3/l09.5 3,280,359 10/1966 Maloney et al. 313/1095 3,406,288 10/1968 Du Bois,Jr.,et al. 313/1095 X 3,508,101 4/1970 Tanji 3 l 3/1095 Primary ExaminerRoy Lake Assistant ExaminerPalmer C. Demeo AttorneyChittick, Pfund, Birch, Samuels & Gauthier PATENTEDNUV 9 IHH SHEET 2 OF 2 MIKIIIARU TANJI INVENTOR "QQAL ATTORNEY CHARACTER-INDICATING ELECTRON TUBE WITH FLUORESCENT DISPLAY STRUCTURE CROSS REFERENCE TO RELATED APPLICATION This application is in part a continuation of the applicants copending application, Ser. No. 676,580, filed Oct. 19, 1967, now US Pat. No. 3,508,101.

BACKGROUND OF THE INVENTION This invention relates to a novel fluorescent display tube.

As is well known in the art a fluorescent display tube generally comprises an insulating base, an anode formed of a plurality of fluorescent segments of a phosphor substance and disposed on the surface of the substrate, a screen grid electrode closely placed on the substrate and perforated at portions corresponding to the regions of respective fluorescent segments, a mesh control electrode disposed in front of the screen grid electrode to diverge and control an electron flow, and a cathode electrode in front of the control electrode.

More particularly, as diagrammatically shown in FIG. 1, applicants prior fluorescent display tube comprises an anode electrode including a plurality of anode segments 1 forming a selected luminous character (or digit or pattern) and embedded in an insulating substrate 2. Although not shown in the drawing, a lead wire is connected to the rear side of each segment 1 to apply an anode potential. On the front side of the insulating substrate 2 is bonded a screen grid electrode 4 formed with windows 3 facing respective anode segments 1 and having the same area as the corresponding anode segment. The screen grid electrode 4 functions to shape segments of the character to be displayed and to collect vapor of the material comprising the anode segments and secondary electrons emitted therefrom. Since the screen grid electrode 4 functions to shape the segments of the character a form of bridge will be formed between each one of windows 3 and a corresponding segment so that during assembling it becomes difficult to correctly align the insulating bridge between respective anode segments on the insulating substrate 2 and the bridges between respective windows of the electrode 4. Further, as shown in FIG. 1, a mesh-shaped control electrode 5 is disposed between a cathode electrode 6 and the screen grid electrode 3 to diverge and control the flow of electrons flowing from the cathode electrode to the anode electrode. In applicants prior copending application the screen grid electrode 4 and the mesh-shaped control electrode 5 are maintained at the same potential to cause the tube to act as a triode. Actually, however, the tube is of the tetrode construction.

SUMMARY OF THE INVENTION One object of this invention is to provide a novel fluorescent display tube wherein a prior art screen grid electrode and a mesh control electrode are combined into a single grid electrode thus acting as a triode.

Another object of this invention is to provide an improved fluorescent display tube in which the single grid which provides the function of both prior art screen grid electrode and mesh control electrode does not have any bridge corresponding to the insulating bridges between luminous segments thus greatly simplifying assembling of the display tube.

Yet another object of this invention is to provide a fluorescent display tube of small size but manifesting good cutoff characteristics.

According to this invention, these and other objects are accomplished by providing a fluorescent display tube comprising an insulating substrate, an anode electrode including a plurality of fluorescent anode segments adapted to form characters or digits, the anode segments being mounted on the insulating substrate and are insulated from each other, a single grid electrode disposed close to the anode segments and a filament extending in front of the grid electrode. The grid electrode is provided with a window common to the region of a pattern formed by the plurality of fluorescent anode segments and the window is provided with an electroconductive mesh.

The single grid electrode provides the function of a control grid that controls the divergence and flow of electrons and that of a screen grid electrode that collects substances evaporated from fluorescent anode segments and secondary electrons emanated therefrom. Thus, the novel fluorescent display tube can act as a tetrode in spite of its triode construction.

BRIEF DESCRIPTION OF THE DRAWING The construction and operation of the novel fluorescent tube can be better understood from the following detailed description taken in conjunction with the accompanying drawing in which:

FIG. 1 is a diagrammatic representation of a fluorescent display tube disclosed in applicant's cited copending application;

FIG. 2 is a diagrammatic representation of an improved fluorescent display tube embodying this invention;

FIG. 3 is a perspective view, partly broken away, of a fluorescent tube embodying this invention;

FIG. 4a is an enlarged perspective view of a control electrode constructed in accordance with this invention;

FIG. 4b is an enlarged plan view of the portion IS in FIG. 4a;

FIG. 5 is a plan view of a luminous anode electrode of the fluorescent display tube; and

FIG. 6 is a plan view of the assembly of the grid electrode shown in FIG. 4a and the luminous anode electrode shown in FIG. 5.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the accompanying drawing, FIG 2 shows an arrangement of electrodes of the novel fluorescent display tube comprising fluorescent segments I which act as an anode electrode and are embedded in an insulating substrate 2 in the same manner as in the prior art construction. Close to the front side of the substrate 2 is disposed a grid electrode 7 constructed in accordance with this invention. The grid electrode 7 is provided with a plurality of windows corresponding to respective luminous segments and each window is formed with a mesh 8 as an integral part of the grid electrode 7. Like FIG. I a cathode electrode in the form of a filament 6 is provided in front of the grid electrode 7.

FIG. 3 shows a perspective view, partly broken away, of a fluorescent display tube embodying this invention and including an evacuated envelope 9 and a getter 10 contained therein. An insulating substrate 2 into which fluorescent segments 1 acting as the anode electrode are embedded is mounted in the envelope and a grid electrode 7 is bonded to the front surface of the insulating substrate 2. A filament 6 acting as a cathode electrode is provided to extend in front of the grid electrode 7. Like a well-known electron tube respective fluorescent segments 1, grid electrode 7 and filament 6 are connected to terminals 11 for connection with a suitable source not shown.

FIG. 4a shows a perspective view of the grid electrode 7 constructed in accordance with this invention. The grid 7 is formed of a metal plate 7 provided with a window 12 of a pattern configuration comprised by all segments of a character to be displayed. As shown in FIG. 4b, the window 12 is provided with a mesh 13 which is formed by etching the metal plate comprising grid 7, of by bonding a metal mesh to the window 12. Alternatively, the mesh may be formed by a pressworking. Perforations 14 are provided for the purpose of positioning the grid electrode for assembly with the anode electrode in a manner to be described later.

A pattern of a group of luminous segments on the insulating substrate is shown in FIG. 5. Fluorescent segments a through j are used to display digits of 0 through 9, these segments being isolated from each other in the same manner as the anode segments in the conventional fluorescent display tube. A segment k is added to display a decimal point. Projections 14' are formed on the substrate to engage guide openings 14 of the metal plate described in connection with FIG. 4a.

ln assembling grid electrode 7 shown in FIG. 4a with the anode electrode shown in FIG. 5, projections 14' are fitted in guide openings 14 is above described to bring grid electrode 7 close to the insulating substrate 2 thus providing an assembly as shown in FIG. 6. Filament 6 is then mounted to extend in front of the assembly and lead wires are connected to respective electrodes. The assembly is then sealed in the glass envelope 9 to complete the fluorescent tube shown in FIG. 3.

As above described the function of a control grid that controls the divergence and flow of electrons and that of a screen grid electrode that collects the substances evaporated from fluorescent anode segments and secondary electrons emanated therefrom are provided by a single grid electrode. As a result, the number of electrodes is decreased by one thus providing an inexpensive fluorescent display tube wherein electrodes can be assembled readily.

The grid electrode employed in this invention has a window of a configuration of a pattern comprised by all fluorescent segments on an insulating substrate and a mesh is formed in the window. Furthermore, different from a prior screen grid, as there is no bridge in the window corresponding to and aligning with the insulating bridges between segments on the insulating substrate, it is not necessary to take care to align the window with the insulating bridge on the insulating substrate, thus rendering easy assembling. This construction also eliminates the provision of a control grid between the screen grid and the filament which was essential to the prior construction so that it becomes possible to dispose the filament closer to the anode electrode thus flattening and miniaturizing the display tube. The cutoff characteristics of the novel display tube has been improved about 30 percent over the prior fluorescent display tube.

What is claimed is:

1. A fluorescent display tube comprising an evacuated sealed envelope, an insulating substrate within said envelope, an anode electrode including a plurality of fluorescent anode segments adapted to form characters, said anode segments being mounted on said insulating substrate and insulated from each other, a single grid electrode disposed close to said anode segments, and a cathode filament extending in front of said grid electrode, said grid electrode being provided with a window common to the region of a pattern formed by said plurality of fluorescent anode segments, said window being provided with an electroconductive mesh.

2. The fluorescent display tube according to claim I wherein said grid electrode comprises a metal plate provided with a window of a configuration corresponding to a pattern formed by all segments of a character to be displayed and a metal mesh provided for said window and wherein said anode comprises a plurality of fluorescent anode segments embedded in said insulating substrate and insulated from each other, said anode segments being arranged to be combined to display a desired character or digit and wherein said grid electrode and said anode electrode are assembled together.

3. The fluorescent display tube according to claim I wherein said grid electrode and said substrate are connected together by means of interfitting projections and openings.

@ 3 3? UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,619,694 Dated November 9, 1971 InventorQs j Mikiharu Tanji It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 1, line 5, after "of" omit "the".

Column 1, line ll, delete "is well known in the art" and substitute therefor disclosed and claimed in applicant's copending application Column 2, line 63, change "of" to or Signed and sealed this 16th day of May 1972.

(SEAL) Attesb:

EDWARD PLFLETCHERJR. ROBERT GOTTSCHALK Attestlng Officer Commissioner of Patents 

1. A fluorescent display tube comprising an evacuated sealed envelope, an insulating substrate within said envelope, an anode electrode including a plurality of fluorescent anode segments adapted to form characters, said anode segments being mounted on said insulating substrate and insulated from each other, a single grid electrode disposed close to said anode segments, and a cathode filament extending in front of said grid electrode, said grid electrode being provided with a window common to the region of a pattern formed by said plurality of fluorescent anode segments, said window being provided with an electroconductive mesh.
 2. The fluorescent display tube according to claim 1 wherein said grid electrode comprises a metal plate provided with a window of a configuration corresponding to a pattern formed by all segmenTs of a character to be displayed and a metal mesh provided for said window and wherein said anode comprises a plurality of fluorescent anode segments embedded in said insulating substrate and insulated from each other, said anode segments being arranged to be combined to display a desired character or digit and wherein said grid electrode and said anode electrode are assembled together.
 3. The fluorescent display tube according to claim 1 wherein said grid electrode and said substrate are connected together by means of interfitting projections and openings. 